Library apparatus having recording medium entry and ejection units

ABSTRACT

A magnetic tape library apparatus having a magnetic tape cartridge entry unit and an automatic cartridge ejection includes a cell unit having a plurality of cells each accommodating a magnetic tape cartridge, a magnetic tape drive unit for writing and reading data to and from any one of the magnetic tape cartridges, and an accessor for automatically switching magnetic tape cartridges between cell unit and magnetic tape drive unit. The magnetic tape cartridge entry unit of the library apparatus includes a stacker for stacking a plurality of magnetic tape cartridges entered externally, and a delivery mechanism for delivering to the accessor each cartridge separated from the stacked cartridges in the stacker. The automatic cartridge ejection unit receives the cartridge from the accessor and transports it to an appropriate position for delivery onto a tray.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a recording medium libraryapparatus. More particularly, the invention relates to a magnetic tapelibrary apparatus having magnetic tape cartridge entry and ejectionunits.

2. Description of the Related Art

Magnetic tape units are one of diverse kinds of external storage devicesfor use with computers. The magnetic tape units operate most commonly onwhat is known as the open reel System using 0.5-inch wide tapes. Thechores of manually loading the open reels have been alleviated bywidening acceptance of automatic tape loading devices. Today, operators'burdens are further alleviated by the widespread use of magnetic tapecartridges. A magnetic tape cartridge, accommodating a tape having thesame width as that of open reel tapes, allows the tape to be threadedout of the reel within for automatic tape loading.

A plurality of magnetic tape cartridges needed are entered in themagnetic tape library apparatus. Any one of the cartridges is selectedand loaded to a magnetic tape drive unit for data recording andreproduction. The magnetic tape library apparatus comprises a cell unithaving a plurality of cells each accommodating a magnetic tapecartridge; a magnetic tape drive unit for recording and reproducingdata; and an accessor for automatically switching magnetic tapecartridges between cell unit and magnetic tape drive unit. The magnetictape library apparatus further comprises a cartridge entry unit forentering magnetic tape cartridge into the library apparatus and anautomatic cartridge ejection unit for automatically ejecting magnetictape cartridges from inside the library apparatus. Magnetic tape libraryapparatuses of this kind are widely used as an external mass storagedevice for computers. These apparatuses are required to operateunfailingly when unattended.

Cartridge entry units proposed so far have failed to give sufficientconsideration to the relations between the disposition of the accessorand the structure of the cartridge entry unit. That is, each magnetictape cartridge entered into the conventional cartridge entry unit isrotated 90 or 180 degrees by a rotation mechanism therein for deliveryto the accessor. This necessitates a complicated structure of thecartridge entry unit, which in turn requires enlarging the libraryapparatus in scale. In addition, it takes time for the rotationmechanism to rotate the entered magnetic tape cartridge. That means moretime required for cartridge entry processing.

The typical prior art automatic cartridge ejection unit comprises a pairof catch arms rotatably attached at one end thereof to shafts, aplurality of feed rollers attached rotatably to the catch arms, and atray assembly for carrying the cartridge released by the catch arms. Thetips of the catch arms have guide members that allow the catch arms tocatch the cartridge horizontally. One disadvantage of this prior artstructure is that cartridges cannot be transported stably inside theapparatus because it is difficult for the catch arms to grip eachcartridge with a uniform force. Another disadvantage is that the catchmechanism tends to be large in scale because each catch arm is supportedrotatably by,its corresponding shaft.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a libraryapparatus having a reliable recording medium cartridge entry unit of asimple construction.

It is another object of the invention to provide a library apparatushaving an automatic recording medium ejection unit which is simple inconstruction and which ejects cartridges in a stable manner.

In accordance with an aspect of the present invention, there is provideda library apparatus comprising: a cell unit having a plurality of cellseach accommodating a recording medium cartridge; a recording mediumdrive unit for writing and reading data to and from any one of therecording medium cartridges; an accessor for automatically switchingrecording medium cartridges between the cell unit and the recordingmedium drive unit; and a cartridge entry unit for entering recordingmedium cartridges into the library apparatus, the cartridge entry unitincluding: a stacker for stacking a plurality of recording mediumcartridges; stage means for carrying the recording medium cartridgesstacked in the stacker, the stage means being arranged to move up anddown: hook means for separating the lowest-positioned cartridge from therecording medium cartridges placed on the stage means; and deliverymeans for delivering to the accessor the recording medium cartridgeseparated by the hook means, the delivery means being arranged toexecute the delivery without altering the orientation of the separatedrecording medium cartridge as i was stacked in the stacker.

In a preferred structure according to the invention, the cartridge entryunit includes shutter means located in the position where the deliverymeans delivers the cartridge to the accessor, and a gate sensor fordetecting a faulty entry of any cartridge placed onto the stacker. Thecartridge entry unit according to the invention eliminates the need fora cartridge rotation mechanism because the unit delivers to the accessorthe cartridge without altering its orientation in effect when thecartridge was placed in the stacker,

In accordance with another aspect of the present invention, there isprovided a library apparatus comprising: a cell unit having a pluralityof cells each accommodating a recording medium cartridge; a recordingmedium drive unit for writing and reading data to and from any one ofthe recording medium cartridges; an accessor for automatically switchingrecording medium cartridges between the cell unit and the recordingmedium drive unit; and an automatic cartridge ejection unit forautomatically ejecting recording medium cartridges from inside thelibrary apparatus, the automatic cartridge ejection unit including:cartridge transport means for receiving the recording medium cartridgedelivered by the accessor, transporting the delivered cartridge to apredetermined position and releasing the cartridge therein; and a trayassembly disposed under the cartridge transport means for carrying therecording medium cartridge released by the cartridge transport means,the tray assembly comprising a pair of side walls, a rear wall, a trayfurnished in a vertically movable manner along the rear wall, anddriving means for moving the tray vertically.

In another preferred structure according to the invention, the cartridgetransport means comprises: a pair of L-shaped catch arms of whichintermediate positions are pivotably mounted to a frame, one end of onecatch arm being pivotably coupled to one end of the other catch arm; aplurality of feed rollers attached rotatably to the other end of each ofthe two catch arms; and driving means for opening and closing the catcharms. Because each ejected cartridge is caught by the two L-shaped catcharms of which the intermediate positions are pivotably mounted to aframe, the cartridge ejecting operation is carried out in a stable andunfailing manner.

The above and other objects, features and advantages of the presentinvention and the manner of realizing them will become more apparent,and the invention itself will best be understood from a study of thefollowing description and appended claims with reference to the attacheddrawings showing some preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of a magnetic tape library apparatusembodying the invention;

FIG. 2 is a rear perspective view of the embodiment of FIG. 1;

FIG. 3 is a schematic plan view of the embodiment with a top plate ofits housing removed;

FIG. 4 is a schematic perspective view showing the inside of theembodiment;

FIG. 5 is a schematic perspective view of an accessor drive mechanism;

FIG. 6A is an external perspective view of a magnetic tape cartridge;

FIG. 6B is a bottom view of the magnetic tape cartridge;

FIG. 7 is a front view of a magnetic tape cartridge entry unit accordingto an embodiment of the invention;

FIG. 8 is a view showing the path through which a cartridge istransported by the magnetic tape cartridge entry unit;

FIGS. 9A and 9B depict how a gate sensor mechanism of the embodimentworks, FIG. 9A showing a cartridge being erroneously entered, FIG. 9Bdepicting a cartridge being normally entered;

FIGS. 10A through 10C are plan views of the gate sensor mechanism, FIG.10A showing a cartridge being entered inversely, FIG. 10B depicting acartridge being incompletely entered, FIG. 10C portraying a cartridgebeing normally entered;

FIG. 11 is a schematic plan view of a hook mechanism according to anembodiment of the invention;

FIGS. 12A and 12B are schematic front views of the hook mechanism in thecartridge entry unit, FIG. 12A showing the hooks being opened, FIG. 12Bdepicting the hooks being closed;

FIGS. 13A and 13B are schematic front views of the stage and hookmechanisms in the cartridge entry unit, FIG. 13A showing the stage atits highest position, FIG. 13B depicting the stage at its lowestposition, with the lowest-positioned cartridge being separated from theother cartridges;

FIGS. 14A and 14B are schematic side views of a feeder mechanism in thecartridge entry unit, FIG. 14A showing the feeder being opened, FIG. 14Bdepicting the feeder being closed;

FIG. 15A and 15B are schematic side views of a shutter mechanism in thecartridge entry unit, FIG. 15A showing the shutter being opened, FIG.15B portraying the shutter being closed;

FIG. 16 is a front view of an automatic cartridge ejection unitaccording to an embodiment of the invention;

FIG. 17 is a side view of a cartridge transport mechanism of theembodiment as it grips a cartridge;

FIG. 18 is a side view of the cartridge transport mechanism as itreleases a cartridge;

FIG. 19 is a longitudinal sectional view of a tray assembly in theautomatic cartridge ejection unit;

FIG. 20 is a partially broken front view of a tray driving mechanism;

FIG. 21 is a partially broken longitudinal sectional view of the trayassembly disposed in connection with the tray driving mechanism;

FIG. 22 is an enlarged schematic view of cartridges as they are stackedon the tray assembly of FIG. 19; and

FIG. 23 is a longitudinal sectional view of another tray assemblyaccording to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a front perspective view of a magnetic tape library apparatus2 practiced as one preferred embodiment of the invention, and FIG. 2 isa rear perspective view, of the embodiment. A housing 4 of the magnetictape library apparatus 2 has at its front a cartridge entry opening 6, acartridge exit opening 8 and a operation panel 7 and 9. The cartridgeentry opening 6 is capable of admitting up to, say, 10 magnetic tapecartridges at a time. The cartridge exit opening 8 stacks up to, say, 15cartridges at a time. At the back of the housing 4 are an operationpanel 11 and a mass cartridge entry/ejection mechanism 10 that places alarge number of cartridges into a row of cells in a cell drum, to bedescribed later.

In FIGS. 3 and 4, a cell drum 12 is attached to a rotary shaft 14, thedrum having a plurality of cells 18 separated by partitions 16. Adjacentto the cell drum 12 are two magnetic tape drive units 28 for writing andreading data to and from magnetic tapes. Between the cell drum 12 andthe magnetic tape drive units 28 is an accessor 20 that automaticallyswitches magnetic tape cartridges 30 therebetween; the cartridges 30 areto be loaded into the magnetic tape drive units 28 for read and writeOperations. In FIG. 3, reference numeral 32 indicates a cartridgeentry/exit unit continued to the cartridge entry opening 6 and thecartridge exit opening 8 of FIG. 1; reference numeral 34 denotes acontrollers.

The driving mechanism of the accessor 20 is constructed as shown in FIG.5. A driving pulley 38 and a driven pulley 40 are attached rotatably toan approximately C-shaped support member 36. A timing belt 42 isthreaded around the pulleys 38 and 40 in an endless manner. The C-Shapedsupport member 36 is secured with a guide member 22 extendingperpendicularly. Another support member 24 is fixed to the timing belt42. One end of the support member 24 is engaged with the guide member22. A hand mechanism 26 with a grip hand 25 is mounted on the supportmember 24.

When a motor 44 is activated, the support member 24 fixed to the timingbelt 42 moves up and down, guided by the guide member 22. That in turnmoves vertically the hand mechanism 26 mounted on the support member 24.When a motor 46 is activated, the support member 24 swings horizontally,with the guide member 22 acting as the center of the swing motion. Thatis, the hand mechanism 26 also swings horizontally. Where the motors 44and 46 are activated selectively under appropriate control, the handmechanism 26 is led to gain access to a selected cell 18 in the celldrum 12 as well as to a selected magnetic tape drive unit 28.

The drive mechanism of the accessor 20 is appreciably simplified becauseit is composed only of the above-described vertical direction drivingmechanism and of the swing mechanism centering on the guide member 22.In practice, the cell drum 12, magnetic tape drive units 28 andcartridge entry/exit unit 32 are located around the accessor 20 in sucha manner that largely the swing motion of the accessor 20 alone (alongwith a limited vertical movement) will effect delivery of magnetic tapecartridges among these components.

Referring to FIGS. 6A, a tape reel 52 is housed rotatably inside amagnetic tape cartridge 30. The base of a magnetic tape 54 is secured tothe tape reel 52, and the intermediate tape portion starting from thebase is wound around the reel 52. The tip of the magnetic tape 54 isequipped fixedly with a leader block 56. The leader block 56 has anengagement groove 56a with which a sled pin Of the magnetic tape driveunit 28 is to be engaged. A cutout 58 is formed in one corner of themagnetic tape cartridge 30. As shown in FIG. 6A, the magnetic tapecartridge, 30 has on its top a depression 51 on which a label is pasted.The bottom of the cartridge 30 has a pair of parallel ridges 53, asdepicted in FIG. 6B.

FIG. 7 is a front view of a cartridge entry unit 68 for enteringmagnetic tape cartridges into the magnetic tape library apparatus 2. Thecartridge entry unit 68 comprises a stacker 70 for stacking a pluralityof magnetic tape cartridges, a stage mechanism 72, a hook mechanism 74,a feeder mechanism 76, a gate sensor mechanism 78 and a shuttermechanism 80. The stacker 70 is a box-like part that admits a pluralityof magnetic tape cartridges 30 entered by an operator. The stacker 70 isconnected to the cartridge entry opening 6 shown in FIG. 1. Cartridges30 entered into the stacker 70 are stacked thereby onto a stage 82 ofthe stage mechanism 72. The gate sensor mechanism 78 checks to see ifthe stacked cartridges 30 are correctly entered.

As will be explained later in more detail, the stage mechanism 72 movesthe stage 82 up and down. The hook mechanism 74 separates thelowest-positioned cartridge alone from the remaining multiple cartridges30 stacked on the stage 82. The feeder mechanism 76 transports to theaccessor 20 the single cartridge 30 separated from the cartridge stackby the hook mechanism 74. The shutter mechanism 80 stops temporarily thecartridge fed by the feeder mechanism 76 so as to keep the cartridgefrom falling off the feeder mechanism 76.

FIG. 8 is a view showing the path through which a cartridge istransported by the magnetic tape cartridge entry unit. The cartridge 30is entered into the stacker 70 in the arrowed direction M with itscutout 58 facing the front right side. Inside the stacker 70, thelowest-positioned cartridge alone is separated from those thereabove bythe stage mechanism 72 and hook mechanism 74, to be described later inmore detail. The separated cartridge 30 is transported by the feedermechanism 76 in the arrowed direction N with the direction of thecartridge at its entry kept unchanged. After getting stopped temporarilyby the shutter mechanism 80, the cartridge 30 is delivered to theaccessor 20.

The gate sensor mechanism 78 for detecting a faulty entry of cartridgeswill now be described with reference to FIGS. 7, 9A and 9B. As shown inFIG. 7, a gate actuator 60 is fed to a shaft 61 which is supportedrotatably adjacent to one side of the stacker 70 and which extends inthe vertical direction. The gate actuator 60 extends along the entirelength of the stacker 70 and is rotatably biased with a spring 62 in thearrowed direction R. The top of the gate actuator 60 is equipped with aflag piece 64. A transmission type photo sensor 65 having alight-emitting diode 66 and a photo-diode 67 is provided in the positioninto which the flag piece 64 may be inserted.

With no cartridge entered, the gate actuator 60 remains pushed by thespring 62 to rotate sufficiently in the arrowed direction R. In thisstate, the photo-diode 67 receives light from the light-emitting diode66 and turns on the photo sensor 65. When the cartridge 30 is entered,the gate actuator 60 is pushed by the cartridge to rotate clockwise.

If the cartridge 30 is not fully entered into the stacker 70 or isentered in an incorrect direction, the gate actuator 60 is pushed by theerroneously entered cartridge to rotate clockwise. This causes the flagpiece 64 to be inserted into the photo sensor 65 before the gateactuator 60 stops. In this state, the flag piece 64 shields light fromthe light-emitting diode 66 and thereby turns off the photo sensor 65.The faulty entry of the cartridge 30 is thus detected.

When the cartridge 30 is entered fully into the stacker 70 in thecorrect direction, the cutout 58 on the cartridge 30 allows the gateactuator 60, which was rotated clockwise earlier by the push from thecartridge 30, to rotate counterclockwise, i.e., in the arrowed directionR pushed by the spring 62. The action pulls the flag piece 64 out of thephoto sensor 65 and thereby turns it off. This allows the normal entryof the cartridge 30 to be detected. At this point, the cartridge 30 islocked to prevent its inadvertent fall from the stacker 70 because thegate actuator 60 interferes with the cutout 58 of the cartridge 30.

How the gate sensor mechanism 78 is illustratively practiced will now bedescribed with reference to FIGS. 7 and 10A through 10C. The photosensor 65 is attached to a plate member 63 fixed to the top plateconstituting part of the stacker 70. The photo sensor as practiced herechecks only for a faulty entry of the cartridge 30; whether or not thecartridge 30 is placed on the stage 82 will be detected by a separatelyprovided stage sensor. When the cartridge 30 is stacked on the stage 82,the stage sensor made illustratively of a photo sensor is turned off.This signals the detection of a cartridge entry into the stacker 70.That is, the combination of the gate sensor mechanism 78 with the stagesensor makes it possible to ascertain whether or not a plurality ofcartridges have been entered normally into the stacker 70.

If the cartridge 30 is inserted into the stacker 70 in an incorrectdirection, as depicted in FIG. 10A, the gate actuator 60 is pushed bythe side wall of the cartridge 30 and fails to return to its homeposition. This leaves the flag piece 64 inserted in the photo sensor 65.As a result, the photo-diode 67 does not receive light from thelight-emitting diode 66 and thus turns off the photo sensor 65. Thissignals the detection of a faulty entry of the cartridge 30. FIG. 10Bshows a case in which the cartridge 30 is entered insufficiently intothe stacker 70 in the correct direction; the cartridge 30 has notreached the bottom of the stacker 70. In this case, as with the case ofFIG. 10A in which the cartridge was entered in the reverse direction,the gate actuator 60 fails to return to its home position, leaving theflag piece 64 inserted in the photo sensor 65. Consequently, thephoto-diode 67 does not receive light from the light-emitting diode 66and turns off the photo sensor 65. This also signals the detection of afaulty cartridge entry.

FIG. 10C portrays the cartridge 30 as it is entered correctly into thestacker 70. In this state, the cutout 58 formed in the front rightcorner of the cartridge 30 allows the gate actuator 60, which wasrotated clockwise earlier by the push from the cartridge 30, to returnto its home position urged by the spring 62. The tip of the gateactuator 60 comes into contact with the cutout 58. The contact pulls theflag piece 64 out of the photo sensor 65. Extracting the flag piece 64allows the photo-diode 67 to receive light from the light-emitting diode66, thereby turning on the photo sensor 65. This signals the detectionof a correct entry of the cartridge 30 into the stacker 70. In thisstate, the tip of the gate actuator 60 is kept in contact with thecutout 58 of the cartridge 30 by the spring 62. Thus the cartridge 30 islocked as entered into the stacker 70. A is described, the gate sensormechanism 78 of the embodiment is capable of detecting a faulty entry ofany one of a plurality of (e.g., 10) cartridges 30 entered at a time.

The constitution and operation of the hook mechanism 74 will now bedescribed with reference to FIGS. 11, 12A and 12B. The hook mechanism 74comprises a front hook 100 and a rear hook 102 pivotably attached tobrackets 96 and 98 fixed to an apparatus frame 84. The tips 100a and102a of the front and rear hooks 100 and 102 are bent as illustrated. Asshow in FIG. 11, the hook mechanism 74 has a side hook 105 pivotablyattached at its lower end to the frame. A bracket 109 fixed to the sidehook 105 can come into contact with a roller 107 attached to the rearhook 102. FIG. 11 shows the state in which the hooks 100, 102 and 105are all closed. The side hook 105 is closed by the push from the rearhook 102.

As depicted clearly in FIGS. 12A and 12B, one end of an L-shaped arm 106is attached rotatably to the front hook 100; one end of an L-shaped arm108 is also attached rotatably to the rear hook 102. The other ends ofthe arms 106 and 108 are attached rotatably to eccentrically positionedshafts on a rotor 104. The rotor 104 is fixed to an output shaft 103a ofa hook motor 103, as depicted in FIG. 11.

FIG. 12A portrays the front hook 100 and rear hook 102 rotated in adirection in which the tips of the hooks move away from each other. Withthe roller 107 leaving the bracket 109, the side hook 105 also moves toan opened position. In this state, the hook motor 103 is activated torotate the rotor 104 in the arrowed direction F of FIG. 12A. Therotation of the rotor 104 turns the front hook 100 and rear hook 102 viathe arms 106 and 108 so that the tips of the hooks move closer to eachother. As shown in FIG. 12B, the tips 100a and 102a of the front, hook100 and rear hook 102 are inserted between the lowest-positionedcartridge 30 and the next-lowest cartridge 30. The stacked cartridgesabove the lowest-positioned cartridge 30 are raised therefrom by thehooks by about 2 mm. In this manner, the lowest cartridge 30 isseparated from the remaining cartridges.

The operation of the hook mechanism 74 and the constitution andoperation of the stage mechanism 72 will now be described in detail withreference to Figs. 13A and 13B. A bracket 86 fixed to the apparatusframe 84 supports a shaft 90 rotatably. A gear 88, fixed to the shaft90, engages with a gear 87 coupled to a stage motor, not shown. A stagecam 92 is fixed eccentrically to the shaft 90. A cam follower 94 thatfollows the stage cam 92 is attached rotatably to the stage 82.

FIG. 13A shows the stage 82 at its highest position. The front hook 100,rear hook 102 and side hook 105 are all opened. These hooks are thuspositioned away from the cartridges 30 placed on the stage 82. In thisstate, the stage 82 is pushed to its highest position by the stage cam92. Activating the stage motor in this state causes the stage cam 92 torotate counterclockwise via the gears 87 and 88, whereby the stage 82starts coming down. The cartridges 30 placed on the stage 82 are alsolowered along with the stage. With the stage 82 lowered to its lowestposition, the hook motor 103 is activated to rotate the rotor 104counterclockwise, as depicted in FIG. 12A. This in turn rotates thefront hook 100 and rear hook 102 so that their tips 100a and 102a movecloser to each other. As shown in FIG. 13B, the tips 100a and 102a ofthe front hook 100 and rear hook 102 are inserted between thelowest-positioned cartridge and the second-lowest cartridge stacked onthe stage 82. Then the second-lowest and higher cartridges are lifted byabout 2 mm, as described, whereby the lowest cartridge is separated fromthe remaining cartridges. The gap G of about 2 mm is needed by thefeeder mechanism 76 to transport the separated cartridge 30, as will bedescribed later. If a sufficient gap G is not obtained, thelowest-positioned cartridge 30, after separation from the othercartridges, will interfere with the cartridge immediately above whentransported by the feeder mechanism 76.

The lowest cartridge 30 thus separated is gripped, with its orientationunchanged, by the feeder mechanism 76. The feeder mechanism 76transports the cartridge 30 to the appropriate position for delivery tothe accessor 20. The constitution and operation of the feeder mechanism76 Will now be described with reference to FIGS. 14A and 14B. L-shapedcatch arms 114 and 116 are pivotably attached with pins 115 and 117 tobrackets 110 and 112, respectively. One end of the catch arm 114 iscoupled rotatably with a pin 118 to one end of the catch arm 116. Aplurality of feed rollers 120 are attached rotatably to the top of thecatch arm 114; a plurality of feed rollers 122 are also attachedrotatably to the top of the catch arm 116. An endless belt 130 isthreaded around the feed rollers 122. The catch arm 116 is equipped witha feed motor 124. Activating the feed motor 124 rotates one of the feedrollers 122 via gears 126 and 128.

An actuator member 132 is coupled to the catch arm 116. The tip of theactuator member 132 has two engagement grooves 132a and 132b. The bottomof a support member 134 has an engagement groove 134a. The two ends of acoil spring 136 are engaged with the engagement grooves 132a and 134a. Aself-holding type feeder solenoid 138 is attached to the support member134. A coil spring 14 is disposed between a plunger 139 of the feedersolenoid 138 and the engagement groove 132b of the actuator member 132.

When the solenoid 138 is not magnetized, the actuator member 132 ispulled downward by the coil spring 136. This causes the two catch arms114 and 116 to rotate away from each other. As shown in FIG. 14A, theroller 120 and feed belt 130 are not in contact with the side of thecartridge 30. In this state, momentarily magnetizing the self-holdingtype solenoid 138 causes the plunger 139 to spread the coil spring 140and to raise the actuator member 132 against the force of the coilspring 136. That in turn rotates the two catch arms 114 and 116 towardeach other. As depicted in FIG. 14B, the feed roller 120 and feed belt130 come in elastic contact with the sides of the cartridge 30. In thisstate, activating the feed motor 124 rotates the feed belt 130 totransport the cartridge 30 to the appropriate position for delivery tothe accessor 20.

While the cartridge 30 is being transported to the appropriate positionfor delivery to the accessor 20, an excessively driven feed motor 124can cause the cartridge to fall off the feeder mechanism 76. Such fallis prevented by the shutter mechanism 80 that positions the cartridge 30so as to ensure delivery to the accessor 20. The constitution andoperation of the shutter mechanism 80 will now be described withreference to FIGS. 15A and 15B. A shutter 144 is pivotably attached witha shaft 146 to a bracket 142. A bracket 148 is equipped with a solenoid150. The shutter 144 is rotatably coupled to the solenoid 150 with a pin152. FIG. 15A depicts the shutter 144 as it is lowered after thesolenoid 150 is demagnetized. FIG. 15B shows the shutter 144 rotatedcounterclockwise by a magnetized solenoid 150 to block the transportpath of the feeder mechanism 76.

The solenoid 150 is magnetized at approximately the same time that thefeed motor 124 is activated. The magnetized solenoid 150 turns theshutter 144 counterclockwise to block the transport path of thecartridge 30. Halfway through the transport path of the feeder mechanism76 is a sensor, not shown, which detects passage of the cartridge 30. Apredetermined time (e.g., 0.5 sec.) after passage of the cartridge 30 isdetected by the sensor, the feed motor 124 is deactivated. During thattime, the cartridge 30 collides with the shutter 144, slips for a whileand stops there. Thereafter, the solenoid 150 is demagnetized, and theshutter 144 is rotated back to its lowered position that does not blockthe transport path of the cartridge 30, is shown in FIG. 15A.

Until the accessor 20 comes to fetch the cartridge 30, the feedermechanism 76 keeps the cartridge 30 gripped. The cartridge 30 is heldgripped as follows. First, the self-holding type solenoid 138 ismomentarily magnetized. This raises the plunger 139 and keeps it there.Then the feed roller 120 and endless belt 130 laterally grip thecartridge in elastic fashion. When the accessor 20 has gripped thecartridge 30, the self-holding type solenoid 138 is supplied with acurrent that flows in the direction opposite to that used when theplunger 139 is attracted. The flow of the current releases the plunger139 from its attracted position. With the cartridge 30 thus disengagedfrom the feeder mechanism 76, the accessor 20 grips the cartridge 30 andbrings it to the appropriate cell of the cell drum 12.

How an embodiment of the automatic magnetic tape cartridge ejection unitis practiced will now be described with reference to FIGS. 16 through21. The automatic magnetic tape cartridge ejection unit 160 is connectedto the cartridge exit opening 8 shown in FIG. 1. FIG. 16 is a front viewof the automatic cartridge ejection unit 160 in its entirety. Theautomatic cartridge ejection unit 160 comprises a cartridge transportmechanism 162 and a tray assembly 164 disposed under the cartridgetransport mechanism 162. The cartridge transport mechanism 162 receivesthe magnetic tape cartridge 30 delivered by the accessor 20, transportsthe cartridge 30 to an appropriate position and releases it there. Themagnetic tape cartridge 30 is inserted into the cartridge transportmechanism 162 through an insertion opening 166.

The tray assembly 164 includes a rear wall 168 and a pair of side walls170 and 172. A tray 176 on which to receive the magnetic tape cartridge30 is connected to a tray driving mechanism 205, to be described later,via a pair of longitudinal slits 174 formed on the rear wall 168. Themagnetic tape cartridge 30 is placed on a cartridge-carrying surface176a of the tray 176. The rear wall 168 has a pair of projected guides178 that extend longitudinally.

The constitution and operation of the cartridge transport mechanism 162will now be described with reference to FIGS. 17 and 18. A pair ofL-shaped catch arms 180 are rotatably attached to shafts 182 that aredisposed horizontally. One end of one catch arm 180 is rotatably coupledto one end of the other catch arm 180 with a pin 184. The other ends ofthe two catch arms 180 are each equipped with a guide bracket 186 thatextends horizontally. The guide brackets 186 are in turn provided withfeed mechanisms 192 and 192' which feed the magnetic tape cartridge 30.The right-hand side feed mechanism 192 comprises a plurality of feedrollers 188 and an endless belt 190 threaded around these rollers 188.The left-hand side feed mechanism 192 includes only a plurality of feedrollers 188 attached rotatably to the guide bracket 186.

One catch arm 180 is coupled to an actuator member 194. The actuatormember 194 is connected to one end of a push spring 196 as well as toone end of a release spring 200, as illustrated. The other end of thepush spring 196 is coupled to a self-holding type solenoid 198 thatdrives the catch arms 180. The other end of the release spring 200 isfixed to a frame 201 of the cartridge transport mechanism 162.Magnetizing the solenoid 198 rotates the two catch arms 180 around thehorizontal shafts 182 toward each other. This causes the feed mechanisms192 and 192' at the tips of the catch arms 182 to be pressed against thesides of the magnetic tape cartridge 30, as depicted in FIG. 17.

When the solenoid 198 is demagnetized, the release spring 200 pulls upthe actuator member 194, rotating the catch arms 180 around thehorizontal shafts 182 away from each other. This causes the feedmechanisms 192 and 192' to release the magnetic tape cartridge 30.Adjacent to the actuator member 194 is a sensor 202 that detects themotion of the catch arms 180. An output signal from the sensor 202permits detection of the opened or closed state of the catch arms 180. Afeed motor 204 is provided to drive the feed mechanism 192.

With the magnetic tape cartridge 30 inserted in the insertion opening166, the solenoid 198 is demagnetized, and the two catch arms 180 arerotated away from each other, as illustrated in FIG. 18. When themagnetic tape cartridge 30 is inserted between the two feed mechanisms192 and 192' through the insertion opening 166, the solenoid 198 ismagnetized. This rotates the catch arm 180 toward each other, causingthe feed mechanisms 192 and 192' at the tips of the arms 180 to grip thesides of the magnetic tape cartridge 30 and keep it in an approximatelyhorizontal state.

Then activating the feed motor 204 causes the feed mechanisms 192 and192' to transport the magnetic tape cartridge 30 to the right until theexit position above the tray assembly 164 is reached, as shown in FIG.16. With the exit position attained, the feed mechanism 192 isdeactivated and the solenoid 198 is demagnetized. This allows therelease spring 200 to force the catch arms 180 into rotation away fromeach other, as depicted in FIG. 18. The magnetic tape cartridge 30 thenfalls downward and into the tray assembly 164.

FIG. 19 is a longitudinal sectional view of the tray assembly 164. Asillustrated, a frame 212 is furnished integrally on the rear wall 168.The bottom and the top of the frame 212 have a driving pulley 206 and adriven pulley 208, respectively, both rotatably disposed. An endlessbelt 210 is threaded around the driving pulley 206 and driven pulley208. The tray 176 is fixed to the endless belt 210 with a bracket. Whenthe endless belt 210 is rotated by the driving mechanism 205, the tray176 moves up and down along the rear wall 168.

Referring now to FIGS. 20 and 21, the tray driving mechanism 205includes a motor 216 attached to a bracket 214 fixed to the frame 212. Agear 218, fixed to the output shaft of the motor 126, engages with agear 220 fixed to a shaft 222. A worm gear, not shown, is attachedfixedly to the shaft 222. The worm gear engages with a worm wheel fixedto a shaft 224. Activating the motor 216 to rotate the shaft 222 turnsthe driving pulley 206 attached to one end of the shaft 224, whereby theendless belt 210 is rotated.

As shown in FIG. 21, the tray 176 is fixed to the endless belt 210 usinga bracket 226. Driving the motor 216 moves the bracket 226 fixed to thetray 176 in a vertically sliding manner along a guide 228. The tray 176has on its top the cartridge-carrying surface 176a. The tray 176 isattached slidingly to the rear wall, with the front end of thetray-carrying surface 176a disposed higher than the rear end thereof.

The tray 176 is initially in its raised position so as to receive thecartridge 30 released by the cartridge transport mechanism 162. Theheight of the cartridges 30 stacked on the tray 176 is detected by asensor, not shown, So that the tray 176 is lowered gradually andcorrespondingly. Up to about 15 cartridges 30 are to be stacked on thetray 176. Because the tray 176 is attached slidingly to the rear wallwith the front end of its cartridge-carrying surface 176a elevated, thecartridges 30 placed on the tray 176 will not fall forward.

When cartridges 30 are stacked, the ridges 53 at the bottom of eachcartridge engage with the depression 51 of the cartridge immediatelybelow, whereby the cartridges are supposed to be stacked in a stablemanner. In the tray assembly of FIG. 19, however, the rear wall 168furnished perpendicularly prevents the ridges 53 from engaging snuglywith the depressions 51. As shown in the exaggerated example of FIG. 22,the higher the cartridges 30 are stacked, the more unstable the stackbecomes. An attempt to extract a plurality of stacked cartridges 30 as awhole from the tray assembly 164 can make the stack become unstable andeven topple.

This problem is resolved by another tray assembly according to theinvention. Referring to FIG. 23, this tray assembly 230 has the upperpart of its rear wall 232 tilted slightly backward with respect to theperpendicular direction. The tilt angle is preferably between 5 and 10degrees. A driving pulley 236 is attached rotatably to the bottom of aframe 234 provided integrally on the rear wall. The top of the frame 234has a driven pulley 238 attached rotatably thereto. An endless belt 240is threaded around the driving pulley 236 and driven pulley 238. A tray242 is fixed to the endless belt 240 via a bracket. A tray drivingmechanism 205 is the same in structure and function as the tray drivingmechanism 205 described earlier and will not,be discussed here again.

In the tray assembly 230 of the above-described constitution, eachmagnetic tape cartridge 30 that fell from the cartridge transportmechanism 162 has its ridges 53 engaged snugly with the depression 51 ofthe cartridge immediately below. As shown in FIG. 23, a plurality ofcartridge 30 are thus stacked on the tray 242 in an orderly and stablemanner. Because the stack is so stable, there is little possibility ofthe cartridges 30 accidentally toppling when they are taken as a wholeout of the tray assembly 230. Thus the tray assembly 230 permits mucheasier and more convenient handling of the cartridges 30.

Although the description above contains many specificities, these shouldnot be construed as limiting the scope of the invention but as merelyproviding illustrations of the presently preferred embodiment of thisinvention. For example, the above-described magnetic tape libraryapparatus embodying the invention is not limitative thereof; theinvention may also be applied to library apparatuses handling cartridgesof other recording media.

Thus the scope of the invention should be determined by the appendedclaims and their legal equivalents, rather than by the examples given.

What is claimed is:
 1. A library apparatus comprising:a cell unit havinga plurality of cells each accommodating a recording medium cartridge; arecording medium drive unit for writing and reading data to and from anyone of said recording medium cartridges; an accessor for automaticallyswitching recording medium cartridges between said cell unit and saidrecording medium drive unit; and a cartridge entry unit for enteringrecording medium cartridges into said library appartus, said cartridgeentry unit including: a stacker for stacking a plurality of recordingmedium cartridge so tht each cartridge rests on any cartridge below it,and the lowest cartridge rests on stage means for carrying the recordingmedium cartridge stacked in said stacker, said stage means beingarranged to move up and down; hook means for separating thelowest-positioned cartridge from the recording medium cartridges stackeddirectly on said lowest-positioned cartridge by separating the stackedcartridges and lifting them off of said lowest-positioned cartridge; anddelivery means for delivery to said accessor the recording mediumcartridge separated by said hook means, said delivery means gripping theseparated recording medium cartridge at multiple locations, saiddelivery means being arranged to execute the delivery without alteringthe orientation of the separated recording medium cartridge in effectwhen the carriage was stacked in said stacker.
 2. A library apparatusaccording to claim 1, further comprising:shutter means disposed betweensaid delivery means and said accessor for delaying delivery until theaccessor is in position to accept a cartridge, said shutter meansincluding: a frame; a shutter plate attached rotatably to said frame ata position where said delivery means delivers the recording mediumcartridge to said accessor; and a solenoid for driving said shutterplate.
 3. A library apparatus according to claim 1, further comprisingfaulty cartridge entry detection means within said cartridge entry unitincluding:a gate actuator provided rotatably and positioned adjacent toone side of said stacker and extending in parallel therewith; a flagpiece attached to said gate actuator; said flag piece moving in responseto faulty entry of a cartridge into said cartridge entry unit; and asensor for detecting movement of said flag piece.
 4. A library apparatusaccording to claim 3, wherein each of said recording medium cartridgeshas a cutout in one corner thereof and said faulty cartridge entrydetection means includes biasing means for biasing said gate actuatortoward protrusion into said stacker, said gate actuator coming intocontact with said cutout of any recording medium cartridge enteredcorrectly into said stacker so that the cartridge will be prevented fromgetting dislodged inadvertently.
 5. A library apparatus according toclaim 1, wherein said stage means comprises:a stage for carryingrecording medium cartridges; a stage cam fixed eccentrically to arotation shaft; driving means for driving said rotation shaft; and a camfollower attached rotatably to said stage for following said stage cam.6. A library apparatus according to claim 1, wherein said hook meanscomprises:a frame; a pair of hooks pivotably mounted to said frame atthe bottom of said hook means, each hook having a bent tip; and drivingmeans for rotating the tips of said hooks selectively toward and awayfrom each other.
 7. A library apparatus according to claim 6, whereinsaid driving means comprises:a disc mounted for rotation to said frame;a first arm having one end pivotably mounted to one of said pair ofhooks and the other end pivotably mounted in an eccentric manner to saiddisc; a second arm having one end pivotably mounted to the other hookand the other end in an eccentric manner to said disc; and a motor forrotating said disc.
 8. A library apparatus according to claim 1, whereinsaid delivery means comprises:a frame; a first and a second L-shapedcatch arm of which intermediate positions are pivotably mounted to saidframe; means for pivotably coupling one end of the first catch arm toone end of the second catch arm; a plurality of rollers attachedrotatably to the other end of said first catch arm and to that of saidsecond catch arm; a motor for driving the rollers attached to at leastone of the two catch arms; and driving means for moving the other end ofsaid first catch arm and that of said second catch arm selectivelytoward and away from each other.
 9. A library apparatus according toclaim 8, wherein said driving means comprises:an actuator memberconnected to one of said first and said second catch arms; a firstspring for biasing said actuator member so as to rotate the other end ofsaid first catch arm and that of said Second catch arm away from eachother; a solenoid for biasing said actuator member so as to rotate theother end of said first catch arm and that of said second catch armtoward each other; and a second spring interposed between said actuatormember and said solenoid.
 10. A library apparatus comprising:a cell unithaving a plurality of cells each accommodating a recording mediumcartridge; a recording medium drive unit for writing and reading data toand from any one of said recording medium cartridges; an accessor forautomatically switching recording medium cartridges between said cellunit and said recording medium drive unit; a cartridge entry unit forentering recording medium cartridges into said library apparatus, saidcartridge entry unit including: a stacker for stacking a plurality ofrecording medium cartridges so that each cartridge rests on anycartridge below it, and the lowest cartridge rests on stage means forcarrying the recording medium cartridges stacked in said stacker, saidstage means being arranged to move up and down; hook means forseparating the lowest-positioned cartridge from the recording mediumcartridges stacked directly on said lowest-positioned cartridge byseparating the stacked cartridges and lifting them off of saidlowest-positioned cartridge; and delivery means for delivering to saidaccessor the recording medium cartridge separated by said hook means,said delivery means gripping the recording medium cartridge separated bysaid hook means at multiple locations, said delivery means beingarranged to execute the delivery without altering the orientation of theseparated recording medium cartridge in effect when the cartridge wasstacked in said stacker; and an automatic cartridge ejection unit forautomatically ejecting recording medium cartridges from inside saidlibrary apparatus, said automatic cartridge ejection unit including:cartridge transport means for receiving the recording medium cartridgedelivered by said accessor, transporting the delivered cartridge to apredetermined position and releasing the cartridge therein; and a trayassembly disposed under said cartridge transport means for carrying therecording medium cartridge released by said cartridge transport means,said tray assembly comprising a pair of side walls, a rear wall, a trayfurnished in a vertically movable manner along said rear wall, anddriving means for moving said tray vertically.